Fish liver is usually recovered from entrails in a manual process following cleansing of fish on a fishing vessel. Cleansing fish can be carried out as either a manual or an automatic process, wherein fish are slit along the stomach and all of the entrails are removed in order to detach and separate the liver from the entrails.
If recovery of the liver involves too much labour, it may be decided to allow it to go to waste, because the required labour resources are either too expensive or not available onboard the vessel. Especially with small fish, recovery of the liver would not be profitable.
Accordingly, only fairly small parts of liver from catches at sea are brought into the landing places and exploited commercially.
In order to exploit these valuable resources, efforts have been invested in developing an automatic process, wherein differences in the density of liver relative to the remainder of the entrails are the main principle of the solution.
From e.g. SU 1321394 A1 “Apparatus for separating liver from entrails of dressed fish in fluid medium” and from SU 1127561 A1 “Apparatus for separating products from impurities” it is known to let the entrails float in a fluid, e.g. fresh water or salt water, whereby the difference in density results in the light liver floating free of the entrails and accordingly provides easier gripping access.
Water is also used to keep the liver afloat in SU 1576120 A1 “Device for cleaning fish” in order to cleanse liver from nematodes and the like. Moreover, separation of organic materials having different density makes up the substance of EP 1447007 A1 “A method and a plant for preparing shrimps”, in which shrimp meat, shrimp shells and shrimp eggs are separated from boiled shrimps.
Based on all the patents mentioned above essentially only the apparatus described in SU 1321394 A1 would be able to detach fish liver from entrails, but this apparatus has a very complex structure, and it is doubtful if it would work in the embodiment shown. It is a big disadvantage that in cases where all the entrails would sink due to a high density, the liver would follow the entrails and go to waste, because the apparatus is not provided with means to avoid the liver being carried on by the winged wheel shown (ref. 3).
The density of the entrails of fish varies based on variations of oil content of the liver and the content of the fish stomach, which can be filled with shellfish with a fairly high density. This means that, even in salt water, a big part of the entrails would sink to the bottom.
Moreover it is a disadvantage of the apparatus if there is a desire to use other parts of the entrails e.g. the roe, as it has to be removed before being led to the apparatus. Otherwise it would be carried with the waste material and most likely become crushed by the wing wheels.
The purpose of the present invention is to recover more of the liver than it is possible with known apparatuses.